Traditional integrated steel making processes use ore containing iron oxide (“iron ore”) as feed materials for blast furnaces. The ore is fed into blast furnaces together with a reductant material such as coke and is converted in the blast furnaces into molten iron that is then used in other steel making processes, such as in basic oxygen furnaces to produce various grades of steel.
Iron ore is generally mined and concentrated prior to shipping for use in blast furnaces located at steel mills. The concentration process increases the amount of iron up to about 60 to 65 percent by weight. Since the iron in the iron ore is in the form of iron oxide (Fe2O3), the maximum concentration of iron in pure iron oxide would be 70 percent by weight. The concentrated iron ore will generally have about 1 to 15 percent by weight of inert materials such as aluminum oxide, calcium oxide, silica oxide, magnesium oxide and manganese oxide.
Several processes have been evaluated to make either pig iron or reduced iron products at the source of the ore in efforts to reduce the cost of shipping the iron units to steel mills and foundries that use the iron to make steel and iron products. One approach involves making small or “mini-blast furnaces” at the ore mining location and using the blast furnaces to make pig iron. This approach is currently being done in Brazil in a process that uses wood as the carbon source for the operation of the blast furnaces.
Another approach that is referred to as the ITmk3 Process involves the use of ore combined with a carbon material in a rotary hearth furnace. This process is designed to produce nuggets of iron for direct use in iron and steel facilities.
There are also a number of direct reduced iron processes (DRI) that use methane, coal and other fuels to reduce iron oxides to iron at the source of the ore. The DRI materials are then shipped to iron and steel facilities.
There are economic and operational issues associated with the above-discussed iron production processes which limit their use in the world market. Nevertheless, the basic advantage that can be achieved with making iron at the location of the mine is the prospect of reducing the shipping costs that is associated with the 35 to 40 percent excess weight (non-iron content) of the ore. Another advantage is that the market for pig iron is larger than the market for iron ore, since iron ore is only sold to steel mills with blast furnaces.
U.S. Pat. No. 6,831,939 to Bratina (the present inventor) discloses the use of an induction furnace that is used for processing iron and volatile metal materials to produce hot metal or pig iron while recovering volatile metals. As disclosed, this process was designed and developed for the recovery of valuable components of materials that had previously been classified as waste materials. The process represented by this patent is a continuous process that uses waste feed materials that are a mix of metal oxides and metal halides and a reductant (such as carbon) that produces both iron and volatile metal products, with the volatile metal products being of primary interest.
U.S. Pat. No. 6,136,059 to Zoppi discloses the use of an induction furnace for the sole purpose of processing electric arc furnace (EAF) dust. That is, after Zoppi initially provides a “heel” in the induction furnace that is a half charge of cast iron which is not replenished and is used for the required oxidation and reduction reactions, are pellets of EAF dust that are added together with coal and small amounts of slagging agents. Zoppi mentions that induction furnace of the prior art are generally only used as a smelting means in secondary steel and non-ferrous metals processing.
The present invention provides a method for the production of an iron product from ore containing iron which involves the use of an induction furnace.